Free NCERT Solutions for Class 12 Biology Chapter 11: Biotechnology Principles and Processes in Food Production Free PDF Download
Question 1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
(i) Human insulin – Diabetes
(ii) Human growth hormone – Dwarfism cure
(iii)Blood clotting factor Y1H/IX-Hemophilia
(iv)TPA (tissue plasminogen activator) – Heart attack/strokes
(v) PDGF (platelet derived growth factor) – Stimulates wound healing.
(vi)Interferon – Treatment of viral infection.
(vii) Interleukine – Enhances immune reaction,
(viii) Hepatitis B vaccine – Prevention of infection infection caused due to Hepatitis B Virus.
(ix)Herpes Vaccine – Prevention of infectious disease.
(x) DNase I – Treatment of cystic fibrosis.
Question 2: Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
Name of the Restriction endonuclease enzyme is – Bam H1. It attaches to the site at 5’-GGATCC-3’. This cleaves DNA in these sequences at just after 5’-G on both the strands. The substrate DNA on which it acts-
Question 3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in
molecular size? How did you know?
Enzymes are smaller than DNA as they are proteins and proteins are macromolecules madeup of amino acids which are smaller than nucleotides. Enzymes are proteins and their synthesis is regulated by small portions of DNA, called genes. Three nucleotides in a specific sequence called as codon in mRNA, helping in the coding of one amino acid, which polymerize to form a specific polypeptide chain and later after certain modifications makes protein.
Question 4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
The molar concentration of DNA in human cell is 2 mg/ml of cell extract.
Question 5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
No, eukaryotic cells do not have restriction endonuclease because DNA molecules of eukaryotes are heavily methylated by an enzyme methylase. Methylation protects the DNA from the activity of restriction enzymes. All the restriction endonucleases have been isolated from various strains of bacteria or prokaryotic cells.
Question 6: Besides better aeration and mixing properties, what other advantages do stirred tank
bioreactors have over shake flasks?
Shake flasks are used for growing and mixing the desired materials on a small scale in the laboratory. A large scale production of desired biotechnological product is done by using ‘bioreactors’. Besides better aeration and mixing properties, the bioreactors have following advantages
(i) Small volumes of cultures are periodically withdrawn from bioreactor for sampling.
(ii) It has a foam control system as foam breaker for regulating the foam formed during the process, pH control system and temperature control system.
(iii) Facilitates even mixing and oxygen availability with the help of baffles, throughout the bioreactor.
Question 7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to
create a palindromic sequence by following base-pair rules.
Palindrome nucleotide sequences in the DNA molecule are groups of bases that form the same sequence when read from both the directions as 5’-3’ direction or 3’-5’ direction. These are the sites for action of restriction enzymes. .
Five examples of palindromic DNA sequences are as follows:
Question 8: Can you recall meiosis and indicated at what stage a recombinant DNA is made?
Meiosis I – During Prophase 1, in Pachytene – When recombination nodule appears after synaptonemal complex formation.
Question 9: Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?
A reporter enzyme can be used to differentiate transformed cells by tracking down the activity of its co-responding genes (receptor gene). For e.g., (3-galactosidase (Lac Z) activity is not found in transformed cells so that they appear white in colour. The others, which appear blue in colour, indicate that cells do not carry foreign DNA.
Describe briefly the followings:
(a) Origin of replication
(c) Downstream processing
(a) Origin of Replication: This is a specific sequence in genome from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also responsible for controlling the copy number of the linked DNA. So, if one wants to recover many copies of the target DNA it should be cloned in a vector whose origin support high copy number.
(b) Bioreactor: Bioreactors can be thought of as vessels in which raw materials are biologically converted into specific products by microbes, plant and animal cell and/or their enzymes. The bioreactor provides optimum growth conditions and facilitates achieving the desired products. The most commonly used bioreactor is of stirring type. A stirred tank bioreactor is usually a cylindrical vessel or vessel with a curved base to facilitate mixing of the contents. In the sparged stirred tank bioreactor, sterile air bubbles
are sparged. The stirrer facilitates the mixing and oxygen availability throughout the bioreactor. A bioreactor has an agitator system, an oxygen delivery system, a foam control system, a temperature control system, pH control system and sampling ports.
(c) Downstream Processing: The product obtained is subjected to a series, of processes collectively called downstream processing before it is made into a finished product ready for marketing. The two main processes are separation and purification. The product is then formulated with suitable preservatives. Such formulations have to undergo clinical trials, in case of drugs.
(b) Restriction enzymes and DNA
(a) PCR – Polymerase chain reaction (in vitro method) is a molecular biological technique for enzymatically amplification of a single small strand or few copies of a segment of DNA in several orders of magnitude and millions of copies of that specific DNA sequence in a short time period (approx 2 hrs).
3 steps in PCR are :
(i) Denaturation (at 96 ºC) of desired double strand DNA- to ssDNA.
(ii) Annealing of primer (at 55-65 ºC) to ssDNA (single standard).
(iii) Extension (at 72 ºC)of primer by Taq DNA polymerase isolated from Thermus aquaticus, synthesizing new DNA strands.
Uses – Amplification of desired gene / gene cloning.
Advantage – More output, greater efficiency, less error prone, less human interference and
cyclic and automated.
(b) Restriction enzymes and DNA – Restriction enzymes is a group of enzymes used to cleave or cut DNA strands, each having a characteristics base sequence at which it cleaves known as recognition site or restriction site.
(i) It restricts foreign DNA from entering normal cell by digesting it at various recognition sites. Recognition site is palindromic.
(ii) They are endonuclease and exonuclease both types.
(iii)They produce sticky ends. Cleavage site and recognition site are different from each other. Restriction enzymes therefore are believed to be a mechanism evolved by bacteria to resist viral attack and to help in the removal of viral sequences.
(c) Chitinase – Chitinase is a hydrolytic enzyme that digest or breakdown glycosidic bonds in chitin present in the cell wall of fungal cell and exoskeleton of some animals including worm and arthropods, to facilitate its transformation or digestion.
Question 12: Discuss with your teacher and find out how to distinguish between
(a) Plasmid DNA and Chromosomal DNA
(b) RNA and DNA
(c) Exonuclease and Endonuclease
(a) Plasmid DNA and Chromosomal DNA
|Plasmid DNA||Chromosomal DNA|
|1||Autonomously replicable||Replicates under nuclear control|
|2||Double stranded, circular||Double stranded, circular or linear|
|3||Not attached with histones||Associated with histone proteins.|
|4||Contains few genes for characters|
like antibiotic resistance, fertility
|Contains genes for controlling the|
characters/proteins for the metabolism of cell
(b) RNA and DNA
|1||Ribonucleic acid, containing Pentose|
sugar as Ribose
|Deoxyribonucleic acid, containing Pentose|
sugar as Deoxyribose
|2||Single stranded||Double stranded|
|3||Carry message from DNA->protein||Main genetic material|
|4||Has Pyrimidine base as uracil and|
|Has Pyrimidine base as thymine and cytosine|
|5||Less stable because of the presence of|
2´- OH group of RNA nucleotides
|More stable because of double stranded nature|
and the presence of Thymine
|6||Synthesized by RNA polymerase||Synthesized by DNA polymerase|
(c) Exonuclease and Endonuclease
|1||Cut DNA at ends by removing|
nucleotides from there.
|Cleave DNA from within by removing|
nucleotides at specific positions/sites
|2||Produce blunt ends.||Produces sticky ends.|
|3||They are not restricting the entry of|
|Restrict entry of pathogen.|